Radiation safety concerns the safe use of ionizing radiation. The radiation exposure has to be controlled to protect people and the environment from unnecessary exposure and the damaging effect to the health. Legal regulations require that radiation exposure (individual radiation exposure as well as collective dose) must be kept as low as reasonably achievable.
The electromagnetic spectrum includes x-rays, gamma rays, ultraviolet radiation, visible light, infrared radiation, and radio waves. Additionally, there are several types of particulate radiation e.g., alpha and beta particles. All types of radiation are used in a wide range of medicine, industry, research and communication. Radiation risks can occur due to either long-term low level exposure or short-term high level exposure. A well-functioning dosimetry program is essential for a safe use and for compliance with federal and state regulations.

Three basic rules have to be observed for a safe use of ionizing radiation.

See also Inverse Square Law, Administrative Dose Guidelines and Annual Dose Limit.

Radiographic contrast media (RCM) contributes important information to the diagnostic process. Actual contrast agents are safe drugs. Adverse reactions are rare, the incidence and severity of side effects decrease with the use of nonionic and low-osmolar contrast media. Adverse reactions are diverse, ranging from mild physiological disturbances to very rare life-threatening anaphylactic or anaphylactoid reactions. Users of contrast agents must be aware of the risk factors and be prepared to promptly manage adverse effects.
Side effects that may occur with intravascular administration of contrast agents are also possible after administration by other paths. Increased risk to an adverse reaction includes patients with a history of a previous reaction to a contrast medium, a known sensitivity to iodine, or a known clinical hypersensitivity (bronchial asthma, hay fever, and food allergies).

See also Contrast-Induced Nephropathy, Iodide-Induced Hyperthyroidism and Idiosyncratic Reactions.

(MSDS) Material safety data sheets are the internationally standardized way to document the hazardous properties of chemicals, radioactive materials and other hazardous agents. Chemical companies provide such data sheets, and collections of MSDS sheets are available.

A clinical trial is a controlled study involving human subjects, designed to evaluate prospectively the safety and effectiveness of new drugs or devices or of behavioral interventions.

See also Adverse Reaction and Safety of Contrast Agents.

Different stages of the drug development and approval process in the USA, lead from preclinical trials (testing in animals), first application in humans through limited and broad clinical tests, to postmarketing studies.

	Years	Test Population	Purpose	Success Rate
Preclinical Testing	3.5	Laboratory and animal studies	Assess safety and biological activity	5,000 compounds evaluated
File IND at FDA
Phase I	1	20 to 80 healthy volunteers	Determine safety and dosage	5 enter trials
Phase II	2	100 to 300 patient volunteers	Evaluate effectiveness, look for side effects
Phase III	3	1000 to 3000 patient volunteers	Verify effectiveness, monitor adverse reactions from long-term use
File NDA at FDA
FDA	2.5	Review process / Approval		1 approved
	12 Total
Phase IV	Additional Post marketing testing required by FDA

By Dale E. Wierenga, Ph.D. and C. Robert Eaton
Office of Research and Development
Pharmaceutical Manufacturers Association

'In reviewing this report, it is important to keep in mind the realities of the drug discovery and development process. The U.S. system of new drug approvals is perhaps the most rigorous in the world. On average, it costs a company $359 million to get one new medicine from the laboratory to the pharmacist's shelf, according to a February 1993 report by the Congressional Office of Technology Assessment.'

See also Phase 1 2 3 4 Drug Trials, Clinical Trial, Food and Drug Administration, and European Medicines Agency.